This is one of a series of questions centered around living on a giant tree. The setting/scenario is described below:

In my fantasy world, elves live on a giant tree, very similar in structure to a Banyan Tree. The elves live on the branches of this tree, which average ~300 feet wide. The tree itself is wide rather than high, only extending 600-1000 feet up. The branches are supported by massive aerial roots, as they are in older banyan trees. The elves can descend the trees to the massive fog-covered swamp below, but rarely do, meaning they have to live off of the tree entirely.

This particular question deals with houses and other constructs the elves would have to build, such as a castle (or at least something that serves the same purpose). The problem is that the elves do not have access to metal, rock, or even a lot of soil. I would imagine some soil would accumulate on the tree, but not enough to start building sod houses out of. All they have access to is a lot of wood.

Given their lack of resources, how would my elves build houses and fortifications?

The obvious answer is that they will build out of wood, similar to how the Pilgrims built when they came to America - wooden houses surrounded by a wooden pallisade. I'm wondering if there is a different approach I can take.


  • In addition to the tree itself, a lot of additional plants are growing on the tree. These include bushes, vines, and even other small trees.
  • The massive tree is home to many animals, and bones/hides are definitely available.
  • Water is available, as it collects in pools on the giant tree branches.
  • Metal and rock are available in very limited amounts, as the elves can trade with the occupants of the swamp below. Enough to make a few special tools out of; nowhere near enough to build anything out of.
  • $\begingroup$ The vines could be useful. Lashing stuff together, weaving nets and portcullises. $\endgroup$ Apr 16, 2017 at 15:28
  • $\begingroup$ the big question is what are defending against. If ground dwellers, you defend the ladders up, if from other elves then you need more traditional fortifications. If someone really wants to kill them and not just loot they can light the tree on fire, so they will never be completely safe. $\endgroup$
    – John
    Apr 16, 2017 at 16:03
  • $\begingroup$ Have you considered having your people build in the tree as opposed to on the tree? $\endgroup$
    – ivanivan
    Apr 17, 2017 at 2:37

4 Answers 4


First of all, look up Polynesian history. They build boats, houses and waged war without metal. Weapons were made of wood, bone and teeth.


As for your buildings. What's the purpose of a castle?

In its simplest terms, the definition of a castle accepted amongst academics is "a private fortified residence". This contrasts with earlier fortifications, such as Anglo-Saxon burhs and walled cities such as Constantinople and Antioch in the Middle East; castles were not communal defences but were built and owned by the local feudal lords, either for themselves or for their monarch.

Liddiard, Robert (2005), Castles in Context: Power, Symbolism and Landscape, 1066 to 1500, Macclesfield: Windgather Press Ltd, ISBN 0-9545575-2-2

I figure you just mean a fortification. Fortifications are dictated by the enemy and their weaponry. If your enemy is other elves living on the tree that means they too have limited access to metals. If it's far away empires that bring armored knights and trebuchets it's a very different requirement.

Where do you build fortifications? Generally along an access point. Either to a valley, on a river crossing etc. So for any outside threat that will be the trunks that lead to the ground. Now a vertical surface is easy to defend. The enemy needs to climb, either the surface itself or a flight of stairs. Elevators can be cut down. Even platforms and stairs could be destroyed under a siege.

If your fighting would be within the tree I see fortifications arise on the points used to travel between branches. Generally the trunk as it's the only thing really going vertical. So a fortification around the trunk makes sense. This needs to be a wall and a gate really.

Perhaps with small holes so our defenders can use specialized pikes to stop the enemy from simply bringing some axes.


I think the most sense would be to erect buildings along connections. Branches to smaller branches, branches to trunk etc. It makes little sense to build a house on the middle of a branch. You got no cover, you're in full wind. No go where you got vertical support from other branches or trunks.

I imagine them cutting into the trunk to make something akin to cellars. Then around it you build your building with wood. The important things protected deep within the bark. If you must live in the middle of a branch dig in. Carve a deep trench as the foundation of your home. Then secure a roof above it.

It makes the most sense your people import iron nails. Wooden pegs could get you far, perhaps even bone is an option. But iron nails would be treasured. Perhaps a sign of wealth even.

If your elves are long lived it would also make sense they shape the tree like a bonsai. Young thin branches are pulled and curved into support structures for future buildings. It's a slow process and needs central administration but it would be worth it for a large city.

  • $\begingroup$ I wouldn't go so far as to contradict your vision of things, but pagoda style structures are built almost exclusively without nails of any kinds, simply using removable wooden pegs. If iron were so terribly hard to get, it may not be likely for even the extremely wealthy to use them to build structures. Culturally, I imagine iron nails would feel to them like using hundred dollar bills as toilet paper - funny to talk about, maybe you do it once to prove a point, and then 'get real man, we need that.' $\endgroup$
    – user8827
    Apr 17, 2017 at 2:46
  • $\begingroup$ I wrote wooden pegs right there with a comment about rare nails. $\endgroup$
    – Mormacil
    Apr 17, 2017 at 8:29

First you might want to check out people who have used trees to build things. Namely living root bridges in India--these are often made by Banyan trees and could be a way to connect communities.

Some techniques: Aeroponic culturing This is specifically to do with using roots for shaping. Your elves have to mist those roots with water and plant food in order to maintain and shape them.

Instant Shaping This works best on more flexible type trees and such, like willow.

Gradual Shaping This is likely most of what they will doing. In the real world growing a chair can take from 8-12 years for example. If they've gotten to be experts and/or they use magic, however subtle, perhaps the time can be cut down.

Bayan is great, but, they might find they want harder wood for fortification, in which case, they might graft on other things. I know that you said they never leave the tree, but... there are going to be resources they need, not the least of which is soil--they will likely end up planting things in the trees, and while they might have "fertilizer" they may need to harvest some soil. Same goes for water. While you say some collects in the pods, it will likely not be enough, especially if they use aeroponic culturing.

I can't say specifically how they are going to build for defense because I have no idea what you are wanting to defend against. So in general, you'll want vantage points to attack from, ways to prevent egress (pull up ladders, ways to block or even HIDE the way somehow).

Banyan trees do have one cool advantage--the hollow column that sometimes happens in the center. Because Banyans grow parasitically on host trees, they eventually kill them, the host tree rots, leaving the Banyan intact, but with a hollow center. I think that you could likely use this in some way. The holes aren't always huge, but it's possible to use mirrors and spy glasses at various points to monitor things. If a tree is cultivated over years and has a ginormous one, you can use it for other things--a secure place to attack from and move freely up and down, that kind of thing.


Why do they need to build? Gorillas nest in trees just fine; likewise chimps. Your elves can use natural features of their trees and bunk down in forked branches or other comfy places. If I lived in a tree I would string up a hammock at night because I worry about falling as I battle ninjas in my sleep.

Fortification means a fort which means a wall. The whole concept of a fortification changes when you live in three dimensions. Consider a squirrel. The squirrel nest is not a stronghold. It is a place for babies to keep them from falling out of the tree when they are little. If the squirrel is under attack it uses the tree - moving up, down and laterally, putting wood between itself and its attacker, going places in the tree that the attacker cannot.


I have loved treehouses since I read Below the Root to my students. In this novel, the people lived both in the trees, inside them and under them. I wonder if you should limit yourself to only one scenario. Each huge tree was devoted to a different guild or branch of services. One was the major food provider, one was a temple, and another silk/clothes...

Below the Root is a science fiction/fantasy novel by Zilpha Keatley Snyder, the first book in the Green Sky Trilogy.

Houses/factories/services in and under and on trees makes your world more flexible.


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